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AN4C21
Aeronautical Standard Machine Bolt
Description
Airframe Bolt, Drilled
Specifications
| Country of Origin | USA |
|---|---|
| Distance From Head Largest Bearing Surface To Shank Hole Center | 1.984 inches minimum first hole and 2.016 inches maximum first hole |
| Fastener Length | 2.141 inches minimum and 2.188 inches maximum |
| Features Provided | Finished head |
| Grip Diameter | 0.246 inches minimum and 0.249 inches maximum |
| Grip Length | 1.672 inches minimum and 1.703 inches maximum |
| Hardness Rating | 26.0 rockwell c minimum and 32.0 rockwell c maximum |
| Head Height | 0.140 inches minimum and 0.172 inches maximum |
| Head Style | Hexagon Head |
| Length | 2 3/16 |
| Material | Steel |
| Material Specification | Mil-s-18732 mil spec single material response |
| Min. Tensile Strength (psi) | 125000 pounds per square inch |
| NIIN | 00-156-2278 |
| NSN | 5306-00-156-2278 |
| Shank Unthreaded Hole Diameter | 0.076 inches minimum first hole and 0.086 inches maximum first hole |
| Surface Treatment | Passivate |
| Thread Class | 3a |
| Thread Diameter | 0.250 |
| Thread Direction | Right-hand |
| Thread Length | 0.438 inches minimum and 0.516 inches maximum |
| Thread Qty | 28 |
| Thread Qty Per Inch (tpi) | 28 |
| Thread Series Designator | UNF |
| Thread Size | 1/4 |
| Weight | .005 lb |
| Width Between Flats | 0.428 inches minimum and 0.440 inches maximum |
Cross-reference
No interchangeable or dimensionally similar parts are on record for AN4C21. Try the cross-reference lookup to search by a different part number.
Catalog data updated 2026-07-05. Report a data error